One minor criteria for the diagnosis of systemic mastocytosis (SM) is a serum tryptase >20 ng/mL, which generally reflects mast cell expansion and is a useful marker of mast cell activation by established criteria. Other mediators where no such criteria have been proposed include heparin, histamine, and prostaglandin D2 and some authors have suggested chromogranin A (CgA) should be among these markers based on limited data. In particular, serum levels of CgA, have been reported as fairly specific to mast cells when evaluating patients for mast cell activation. CgA itself is a 439-residue granin family protein (48-60 kD) found in the secretory vesicles of neuroendocrine tissues and is a biomarker for assessment of neuroendocrine tumors. Proton pump inhibitor (PPI) use is associated with an increase in CgA levels, as acid suppression by PPIs promotes hypergastrinemia which leads to increased CgA via gastrin-regulated enterochromaffin-like cells. We thus prospectively determined serum CgA, gastrin and tryptase levels in 20 adults and 17 pediatric patients diagnosed with mastocytosis based on WHO criteria. All patients had symptoms consistent with mast cell activation. Bone marrow, skin and small intestinal biopsies were obtained from patients with indolent SM (ISM). Samples were fixed and stained for tryptase and CgA. HMC1.1, HMC1.2 and LAD2 human mast cell lines and the pancreatic beta islet cell carcinoma line, QGP-1, were used to determine relative quantitative expression of CgA using RT-PCR and Western blotting. We found that both adult and pediatric patients with mastocytosis not taking PPIs have serum CgA levels within the normal reference range and that the serum levels of CgA are significantly influenced by the use of PPIs. Biopsies stained for CgA associated with mast cells were negative. The relative expression of chromogranin by qPCR and western blotting in mast cell lines compared to positive control (QGP-1 cells) was low, even when cells were activated through the IgE receptor. Thus, we found that use of PPIs is the cause of elevated serum CgA in patients with mastocytosis. These results, coupled with other data, demonstrate that mast cells are not a significant systemic source of serum CgA. Therefore, we recommended that serum CgA not be used as a biomarker of mast cell disease, which if widely applied as a recommendation, should result in significant cost savings and help avoid confusion in the use of serum CgA determinations. The culture of mast cells from human tissues such a cord blood, peripheral blood or bone marrow aspirates has advanced our understanding of human mast cells (huMC) degranulation, mediator production and response to pharmacologic agents. However, existing methods for huMC culture tend to be laborious and expensive. Combining technical approaches from several protocols, we designed a simplified and cost-effective approach to the culture of mast cells from peripheral blood and cryopreserved cells from lymphocytapheresis. We significantly reduced the amount of culture media required, while the total MC number generated by this method was similar to previous methods, resulting in significant budgetary savings. We further performed a functional analysis by flow cytometry which maximized the data we could obtain from cultured cells. We believe these approaches will allow more laboratories to culture and examine huMC behavior going forward. Neoplastic accumulation of mast cells in SM associates with activating mutations in the receptor tyrosine kinase KIT. Constitutive activation of tyrosine kinase oncogenes has been linked to imbalances in oxidant/antioxidant mechanisms in myeloproliferative disorders. However, the impact of KIT mutations on the redox status in SM and the potential therapeutic implications are not well understood. We thus examined the regulation of reactive oxygen species (ROS) and of the antioxidant protein DJ-1 (PARK-7), which increases with cancer progression and acts to lessen oxidative damage to malignant cells, in relationship with SM severity. ROS levels were increased in both ISM and aggressive variants of the disease (ASM). However, while DJ-1 levels were reduced in ISM with lower mast cell burden, they rose in ISM with higher mast cell burden and were significantly elevated in patients with ASM. Studies on mast cell lines revealed that activating KIT mutations induced constant ROS production and consequent DJ-1 oxidation and degradation that could explain the reduced levels of DJ-1 in the ISM population, while IL-6, which increases with disease severity, caused a counteracting transcriptional induction of DJ-1 which would protect malignant mast cells from oxidative damage. A mouse model of mastocytosis recapitulated the biphasic changes in DJ-1 and the escalating IL-6, ROS and DJ-1 levels as mast cells accumulate. These findings were reversed with anti-IL-6 receptor blocking antibody. Our findings provide evidence of increased ROS and a biphasic regulation of the antioxidant DJ-1 in variants of SM and implicate IL-6 in DJ-1 induction and expansion of mast cells with KIT mutations. We interpret this data as supporting IL-6 blockade as a potential adjunctive therapy in the treatment of patients with advanced forms of mastocytosis, as it would reduce DJ-1 levels making mutation-positive mast cells vulnerable to oxidative damage. In a general effort, we also assisted in the development of the first mastocytosis quality of life questionnaire for adult patients with cutaneous and indolent systemic mastocytosis. This instrument will serve as a much needed measure of response to medical intervention in future clinical studies and in routine patient care. We further participated in consensus documents which revised the classification of systemic mast cell disorders.